The unimolecular and collision-induced decompositions of (NaF)2Na+ ions formed by excitation of a sodium fluoride surface with 7 keV Xe ions was investigated. By comparing the results with ab initio calculations, it was possible to demonstrate the presence of two structures of this cluster ion, differing in their internal energy content. The lower energy state (i.e., more stable) was similar to that of the crystal structure. By application of a tandem quadruple mass spectrometer system, the conversion of kinetic energy into internal energy was investigated for the molecular ion of 2-pentanone. It was found that between 14 and 25% of the available kinetic energy was converted into internal energy. Onset of conversion to internal energy through an electronically excited state was observed at 2.0 eV. In a second study, it was demonstrated that, at least for [C4R4]+ ions, there exists a Hammett correlation for ratios of intensities of collision-induced fragments on the basis of the statistical theory of mass spectra and in practice. To help define the gas-phase reaction paths leading to the formation and subsequent decomposition of PO3-, the negative chemical ionization mass spectra of a group of dimethylvinyl and dimethylaryl phosphates were obtained, employing a variety of mass-spectral techniques. In every case, a major pathway to P03- appears to consist of the sequence (a) capture of a thermal electron by the molecule, (b) loss of the vinyl or aryl group to produce the dimethyl phosphate anion, and (c) elimination of dimethyl either to yield P03-. This ion, when suitably activated, decomposes further only by losing an oxygen atom to yield P02-, the metaphosphite anion. The mechanism for the substitution reactions of NH3 in the ammonia chemical ionization mass spectra of aromatic esters has been investigated. The formation of the NH3 adduct ion involved the protonated molecule and the formation of an unstable intermediate which then underwent a reactive collision with another NH3 to give the adduct production.